Composite materials are more commonly being used for fabrication of a wide variety of components. For example, carbon fiber composites have high strength and a low weight, making carbon fiber composites attractive for use in aviation applications that require these functionalities. As another example, ceramic matrix composite (CMC) materials can withstand relatively extreme temperatures; accordingly, there is particular interest in replacing components within a combustion gas flow path of a gas turbine engine with components made from CMC materials. Many composite materials, such as carbon fiber and CMC materials, are formed from plies, and the plies may be laid up to form a preform component that may then undergo various processing cycles to arrive at a component made from the composite material.
Typically, composite components made from plies comprise many plies. Each ply is cut from a sheet of (e.g., textile material) and then the cut plies are laid up to form one or more ply stacks that form the component preform. As used herein, a stack or ply stack describes more than one plies placed on each other. Often, the cut plies are manually removed from the sheet and manually placed in a ply storage area or manually stacked. Similarly, components for use in other applications, such as automotive, electronics, and telecommunications applications, may be formed from many stacked cut-outs, which are segments cut from relatively thin materials and may be manually manipulated. Thus, the handling and forming of preforms or cut-out stacks is a time consuming and labor intensive process, which increases the cost of the components.
Automating the removal and storage or stacking of the preform process could reduce the part cost and cycle time, as well as reduce employee health concerns from the repetitive nature of ply removal and handling. However, several barriers must be overcome to automate the process of removing plies from the sheet of material and moving the plies either to a ply storage area or for stacking. For example, to maximize material usage and minimize material waste, a variety of ply shapes and sizes are nested within the sheet and then cut prior to removal. Therefore, an automated apparatus for removing the plies must be able to adapt to a variety of ply shapes. Also, the automated apparatus must be able to remove the ply from the nested plies without displacing the left-over or remaining sheet material. As another example, for large plies, the automated apparatus must be able to maintain the ply in a substantially straight or flat configuration as it is removed and moved to prevent damaging or distorting the ply as it is removed or moved.
Accordingly, an automated cut-out or ply manipulation apparatus that overcomes these and other barriers would be desirable. For example, an end effector for a robotic arm that can grip and remove one or more cut-outs or plies from a sheet of material would be beneficial. In particular, an end effector having a plurality of gripping surfaces such that the end effector may grip cut-outs or plies having a variety of shapes and/or sizes would be useful. Additionally, methods for removing cut-outs or plies using an end effector having a plurality of gripping surfaces would be helpful.